Simultaneous postinfectious glomerulonephritis and thrombotic microangiopathy: a renal biopsy study.

The simultaneous occurrence of postinfectious glomerulonephritis and thrombotic microangiopathy is described in renal biopsy specimens from three patients. Each presented with diverse manifestations: two patients had hypertension and acute renal failure, and in the third, it was unclear whether an atypical postinfectious glomerulonephritis or an atypical thrombotic microangiopathy was present. All biopsy specimens disclosed a combination of irregular granular complement and immunoglobulin deposits in mesangial regions and capillary walls along with fibrin in a linear pattern in capillary walls by immunofluorescence. Light microscopy showed diffuse hypercellularity in some glomeruli, endothelial cell swelling, luminal thrombi and mesangiolysis in others, and both types of changes in a third group. Ultrastructurally, subepithelial hump-shaped deposits coexisted with widened and lucent subendothelial spaces. Possible pathogenic mechanisms for the synchronous lesions include endothelial injury, perhaps triggered by infection and immunologic tissue damage.